A wide variety of applications call for the ability to adjust and maintain the position of two objects relative to each other. Ease of adjustment and ability to hold a position once set are desirable. Additional desirable characteristics of a positioning device include high reliability, compact size and ease of manufacture.
Known positioning and adjustment devices have typically involved the use of a biasing means, such as a spring to control positioning. Springs often increase the effort required to adjust position of objects, because invariably, the operator is working against the spring, often multiple times, during adjustment. Springs are troublesome in that they are prone to wearing out or breaking. Spring failures can result in catastrophic failure of the entire positioning means. Assembly of a positioning device involving a spring can also be problematic and dangerous due to the high forces typically required to compress a spring during assembly of the positioning device.
One application of positioning devices involves furniture, and more specifically, chairs. Adjustment of chair components has long been known to increase comfort and efficiency of workers seated for long periods. A variety of adjustment devices have been used to allow for adjustment of chair components, such as seats, backrests and armrests. However, these devices have typically suffered from the drawbacks involved with reliance on a biasing means.
Similarly, adjustment of machines to adapt to different worker sizes is desirable to increase worker comfort and efficiency. Such applications are also typically disadvantaged by the use of a biasing means.
A need exists for a positioning device that does not involve a biasing means, thereby providing increased usability, reliability and efficiency in manufacture.
According to one embodiment of the invention, a positioning mechanism is provided, having a first member defining a channel, a second member, slidably mounted to the first member along an axis, a substantially non-biased cog, rotatably mounted to the second member, such that the channel and the cog interact to inhibit motion of the second member in a first direction relative to the first member until the second member has traveled substantially in a second direction.
A further, optional aspect of the invention includes a positioning mechanism involving an entry channel, continuous with the channel, to permit entry of the cog into the channel by slidable movement between the first and second members along the axis.
According to a second embodiment of the invention, an adjustment mechanism is providing, having a first member defining a channel, a second member mounted to the first member to be slidable with respect to the first member along an axis, a cog, substantially free of a biasing member and mounted between the first and second members and adapted to rotate with respect to the second member, such that the channel is formed to create locking positions, enabling the cog to inhibit motion of the second member in a first direction relative to the first member.
An optional aspect of the second embodiment of the invention is an undulating surface formed in a side of one of the first and second members, facing an other of the first and second members and oriented parallel to the axis, and a tab, mounted to the other of the first and second members and biased toward the one of the first and second members, adapted to travel along the undulating surface.